Persistent gas flow seen in Bose-Einstein Condensate

Maryland - Researchers at the National Institute of Standards and Technology (NIST) and the Joint Quantum Institute in Maryland, have discovered a way to create a donut-shaped Bose-Einstein Condensate (BEC) exhibiting properties of persistent gas flow. These could have practical applications in future ultra-tiny, ultra-accurate gyroscopes.

BECs are peculiar states of superfluidic matter (matter moves as a fluid without friction) near absolute zero where quantum effects develop into the macro scale. They were first theorized by Albert Einstein in 1925, who built his theory atop previous work of Satyendra Nath Bose—though no BEC matter was ever witnessed in the laboratory until 1995. In this particular case, using a special kind of angular momentum laser pulse to stir the sodium gas in the BEC state, a visible flow is shown to persist for at least 10 seconds after the laser is turned off. This is true even when only 20% of the gas was in the BEC state, raising additional questions about how BECs and superfluids work together.

They key to making this particular experiment work was the donut shape. Previous BECs have been ball-shaped or cigar-shaped. The donut shape created a type of barrier where, unlike normal BEC matter which exhibits the peculiar effect of jumping out of its container in quantum-like ways (basically, it goes where it shouldn’t), a high enough energy level existed between the non-atom hole in the center, and the BEC grouping of atoms, that the material was "coaxed" into staying put in the donut. When stirred, the circular path also provided a natural manner for the gas to move. The laser conveyed angular momentum which, according to the researchers, acted like tiny oars in the water creating eddies. When enough of these were created the fluid began to move uniformly.

Researchers believe this experiment could provide additional information on the fundamental properties of BECs and superfluids. They also believe that in the future, tiny gyroscopes could be created which are extremely sensitive to movement. They point out that there are already BECs on a chip that are targeting this very application. The superfluid motion would be so sensitive that any motion would be detected and potentially measured.

Research was carried out by C. Ryu, M. F. Andersen, P. Clad, V. Natarajan, K. Helmerson and W.D. Phillips. NIST provided funding.